MySQL - Define a variable within select and use it within the same select

Question

Is there a possibility to do something like this?

SELECT 
    @z:=SUM(item),
    2*@z
FROM
    TableA;

I always get NULL for the second col

Answer 1

Works in mysql 5.5

select @code:=sum(2), 2*@code

+---------------+---------+
| @code:=sum(2) | 2*@code |
+---------------+---------+
|             2 |       4 |
+---------------+---------+